


The Interaction of Light with the World

by itcouldallbesosimple



Category: Supergirl (TV 2015)
Genre: Alternate Universe - College/University, F/F, Smut
Language: English
Status: In-Progress
Published: 2021-03-14
Updated: 2021-03-21
Packaged: 2021-03-22 15:20:56
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 19,280
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30040707
Author URL: https://archiveofourown.org/users/itcouldallbesosimple/pseuds/itcouldallbesosimple
Summary: She thinks it sounds like poetry, this course called “The Interaction of Light with the World.” It’s not. It’s a freshman seminar. About physics. And she can’t get out of it.
Relationships: Kara Danvers/Lena Luthor
Comments: 27
Kudos: 138





	1. Water Light Guide

National City University is big. Really big. Way bigger than Metropolis State University and Metro State is a campus of 30,000 undergrads. The north side of campus is host to the university’s state of the art athletics programs. The east side houses dorm after high-rise dorm stuffed to the gills with 18- and 19-year olds and their loft beds and mini-fridges. The west side’s got the architecture school and the ed school and all of the art buildings, plus one of the campus’s biggest libraries. And the south side’s where she’s got most of her classes. It’s a mix of science labs and Art Deco buildings full of seminar rooms, liberal arts lecture halls, university administration buildings, and the J-school. 

That’s how it’s laid out in Kara’s mind, anyway. There’s probably several dozen buildings she’s still missing from her mind map, but she’s got the most important ones memorized. The Aquatic Center (north side) to the Clark building (south side), then to room 131 in the J-school building (south side), then to room 215 in the J-school building (south side again, obviously), then to Campus Center Dining (in the campus center, if you can believe it), then back to the Aquatic Center (north side). It’s a haul on Mondays, Wednesdays, and Fridays and it wasn’t the schedule she wanted, but she had some catching up to do on her journalism major requirements. That, and despite her best efforts, she just couldn’t escape National City University’s mandated freshman seminar, even as a junior transfer. 

She’d pleaded her case over and over, first with the swim team coach (“I know it seems silly, Kara, but my hands are tied. It won’t be that bad.”), then with her advisor (“Just get it over with.”), and finally with the Dean of Students (“We’re really lucky that an athlete as talented as you decided to transfer to NCU, Kara, but there are some rules we just can’t bend. I’d suggest you find a seminar that speaks to you and enjoy the ride.”) She’d pleaded so long that most of the seminars filled up. And certainly the ones “spoke to her” filled up. 

Which is how she finds herself sprinting - literally sprinting - to the Clark building on the first Wednesday morning of classes. 

“Blurred Line: Documenting Truth in Info & Media” was full. “Journeys through Hell” was full (she didn’t even need to read the course description to know that one would have been good). “War Stories: Looking at War through the Tales We Tell” was gone. By the time she had logged into the registrar to officially sign up, out of the three courses that still had open seats, only one seemed even the barest bit intriguing: “The Interaction of Light with the World.” Maybe it’s just her interest in writing that makes her think this, but that line sounds like it belongs in a poem. Except it’s physics. 

She’s only six minutes late when she huffs through the open door. Some of the two dozen or so eyes in the room look up at her, but even more are glancing around the room like they’re hallucinating. For a moment, Kara just pauses in the door, unsure that she even wants to enter. And then a moment later, she wriggles between a pair of chair-desk combos to plop down in a free desk along the back wall. 

She waits a minute, then two. The other students are just staring out the windows and following the shadows on the walls. Freshmen. 

Then, it’s ten past and she just can’t hold it in any more. A room full of freshmen at their first class on their first day of their first year of college can’t possibly know about the rule. 

“Hey, ‘scuse me,” Kara whispers to the kid at the desk next to her. He’s looking out the window and she catches his attention on a repeat whisper. When he turns to face her, he doesn’t speak, just raises his eyebrows. Probably a little shocked that Kara’s so sweaty. 

“Do you know the 15-minute rule?”

His brows tighten into a frown, which Kara takes for a “no.”

“You know we can leave after 15 minutes if the professor doesn’t show, right?” She looks up at the clock on the wall again. Just three more minutes until the 15-minute rule takes effect. 

Kara doesn’t see her until she’s hovering over Kara at the other side of her desk, a gentle hand on Kara’s shoulder and a throaty whisper in her ear. 

“Do you need help on the assignment?” 

It startles her. She’d been so engrossed in thinking about the minute hand hitting the little three and explaining the 15-minute rule to this pimply-faced freshman that she didn’t even notice this  _ absolute knockout _ beside her. Freshman women at NCU must be built different. 

As she turns to face this freshman woman (because only the term “woman” can describe her, not “girl” or “kid”) her jaw drops, her heart drops, her panties would drop if she wore them. “Her boyshorts drop” doesn’t have quite the same ring to it. 

“Um. Assignment?” she squeaks. 

The woman crouches down next to Kara’s desk so that they’re eye to eye and nose to nose and lips to lips. And eyes. And lips. And eyes, no lips. No eyes. Eyes. Stunning green eyes. 

“The assignment. Do you need help with it? It’s just a brainstorming activity: find interactions of light in the room.”

Man this chick is beautiful. It’s probably a little too soon to cajole her into a partner study session (Kara’s go-to pickup at Metro State), but maybe by the third class? 

She decides to plant a seed that she figures she’ll be able to reap in a week or two: “Like the way the light hits your eyes when you crouch down next to me?”

The woman's pale face shades hot pink in an instant. It travels from her cheeks to her neck and down to the alabaster skin peering from the opening of her silk blouse. “Sure,” she replies more hesitantly than Kara would prefer. 

“Okay, uh, thanks. Thanks for your help, I mean.” It’s either the woman’s blush or her clear reluctance or maybe it’s both, but it set off a classic case of the Kara-rambles. “I must have missed that part where the professor gave the assignment,” she continues. “I had to rush over here from swim practice and I’ve never been from the Aquatics Center to this building before and I didn’t realize it would take so long. You can see how sweaty I am. I was sprinting. Golly, and now I’m talking about how sweaty I am…” which is when she trails off as she looks around and now finds every single one of those two dozen or so eyes in the room on her. 

She looks back at the woman, still crouched down beside her, listening intently and asks, “Did the professor step out?” 

The room erupts. She’d swear there were 500 people in the room and not twelve or thirteen, or whatever. A blush blooms on her cheeks to match the blush on the woman’s, who’s not laughing either. 

“I’m the professor,” the woman says as she stands. 

There’s an instant when Kara wants to sprint out of the room in the same way that she came in. But that instant passes, just like the rest of the pile of embarrassing moments she’s racked up in the course of her 21 years, and she lowers her head sheepishly instead. Another classic Kara move. 

“I’m so sorry uh, Dr., uh…”

“Luthor.”

“Right. Crap. I’m so sorry, Dr. Luthor.”

Dr. Luthor just nods as she walks toward the front of the room. 

Kara just barely hears Dr. Luthor’s slight accent hum through an explanation of the syllabus. She catches a note here about a weekly homework assignment and a note there about office hours and a final note about a culminating project. Mostly, though, she’s replaying those three intimate minutes she shared with Dr. Luthor earlier and wondering just how far up Shit’s Creek she’s paddled herself. Kara knows professors can file sexual harassment grievances against students, it was part of her student-athlete orientation. A grievance would lead to a removal from class pending a drawn out administrative hearing. Maybe it’s just wishful thinking on Kara’s part, but that doesn’t seem like a path Dr. Luthor might take. Besides, what she said wasn’t that bad, right? Just a compliment about her eyes. 

She wishes she could resolve not to objectify Dr. Luthor, or at the very least to figure out a way to make her less attractive. Being able to pay attention to a lecture without thinking about those green eyes or the deep curve of her hips or the gravelly tone Kara caught in their private conversation earlier - that would go a long way toward getting an ‘A’ in the class. Instead, she figures this class will be a painful battle of wills between brain and instinct. At the moment, she’s not sure which one she wants to prevail. 

The quiet of the class breaks her from her reverie and she finds Dr. Luthor’s back to the class. There’s one of those matte black lab tables she remembers from high school science classes at the front of the room. On top, there are three objects. On the far right, there’s a clear plastic bin, like the kind she uses to store her sweatpants and sweatshirts during the summer. Next to it, the center object is a cylindrical tube she somehow had not noticed before. And on the other side of the tube is a machine-looking thing Dr. Luthor’s plugging into the front wall. 

When she straightens back up from crouching to plug in the machine, she runs her palms along the sides of her skirt and looks up at the class. 

“The syllabus made clear that every Wednesday I’d share a demonstration, an interaction of light with the world. We’ll do our first demonstration today.”

A hand goes up. There’s a pencil nervously twitching between the fingers that are in the air. 

She freezes for a moment, like she’s not expecting any sort of participation, then slowly nods. 

“Uh, Dr. Luthor? Should we take notes?”

“If you’d like.”

“Will this information be on the final exam?”

“Freshman seminars don’t have final exams.”

“Oh. So what should we take notes about?”

“How about you take notes on the new information you’re learning?” Her tone isn’t mean, exactly, but it is blunt. Or maybe it’s naive. Do 18-year olds take notes just to take notes? Apparently Dr. Luthor thinks so. 

Kara digs through her bag to find a pencil. She’s got two swim caps, a pair of goggles, a t-shirt that still feels a little damp, and about six different kinds of energy bars in there, along with a singular pencil and no paper. She’s a junior. She knows how college works. The first day of classes is for going over the syllabus, not taking lecture notes. It’s another one of those college mores that Dr. Luthor’s blowing off, and on the first day of classes no less. 

Paired with the other events of the morning, Kara feels so keyed up that she wishes she was in the pool instead of gearing up for two more classes and two more hours tucked into these godforsaken chair-desk combos. 

She finally finds a pencil with just enough of a point to write, then flips the syllabus over and is relieved to find a blank page. Taking notes just to take notes is a new one, but Kara thinks she might follow Dr. Luthor on a long walk off a short pier, or straight into the fiery depths of hell, or into a raw vegan diet. They’re all pretty much the same in Kara’s mind. 

“This demonstration is called a water light guide. The phenomenon we’ll see is called ‘total internal reflection.’ Today, we’ll see the demonstration, then discuss it. On Friday, we’ll talk about the theory and we’ll take a closer look at its formula. Now this isn’t meant to be a tremendously rigorous course, but there are lots of different languages we can use to explain the way that the world works - including mathematical models - and I intend to teach them.”

Student-athletes at NCU are expected to maintain a 2.0 grade point average, also known as being a solid ‘C’ student. As a transfer, Kara’s obviously new to NCU, but at Metro State she could reliably depend on an ‘A’ or ‘A-’ in any class that stayed far, far away from anything having to do with numbers. 

Contemporary Wellness Issues: A. (At Metro State, it was a requirement for all student-athletes. Something about “taking care of your bodies.”) In one session of that class, she’d tortured the professor by biting into a big, juicy cheeseburger just as the lecture began. 

Introduction to Storytelling: A+. (After that class, she declared herself a journalism major.)

But, just like at NCU, Metro State had some mandatory courses for freshmen and sophomores. She’d tried to save the four required math and science courses for the spring semesters, usually, when swimming eased up a bit. But even that didn’t help. 

Statistics 101: C. (She’d taken an advanced stats course in high school and figured this one wouldn’t be far off from that one. It was. Far, far off.)

Principles of Economics: C. (Someone had told her that econ wouldn’t involve math at all. They were right, but it did involve  _ numbers _ .)

Business Math: C. (She’d wrongly assumed that business math would somehow be easier than say, Calculus.)

As long as the J-School classes came as naturally to her at NCU as they did at Metro State, she figured she’d be closer to a 3.0 GPA than that dreaded 2.0. But as a transfer to a new school with a stronger academic reputation, she found herself with pencil to paper, just like every one of the freshmen in the room. 

“Rather than explain the demonstration today, I’m just going to show it and talk us through the steps of it. Then, I’ve made sure we have about ten minutes for you to ask questions and for us to discuss observations, which should lead us nicely into our class on Friday. Someone get the lights.”

The room goes dark a moment later. At some point during their review of the syllabus, Dr. Luthor pulled the blinds over the windows. With the lights off, sunlight peaks around the corners of the blinds so that each face in the room seems to be shining in the shadows. Dr. Luthor’s got a special glow to her, Kara thinks. 

But then she realizes that there’s a neon green light emitting from the machine at the front of the room. Ok, so maybe no special glow to her after all. 

“I’ve just turned on this green diode laser that the physics department keeps in storage. I mentioned when I reviewed the syllabus that toward the end of the semester, you and a partner will present your own demonstration of light interacting with the world. This weekend, I’ll post partners for the project along with a list of equipment that you and your partner may check out to conduct your demonstration.”

Kara finds herself writing “green diode laser” and “project” on the back of the syllabus, as though those words will be useful later.

“You may not be able to see it in the back, but can someone at the front of the room share what’s inside of the cylinder?”

A couple tentative hands go up in the front of the room. 

“Please, just speak. You’re in college now,” Dr. Luthor says and Kara stifles a chuckle.

Freshmen.

“Clear liquid.”

“But it’s like, sort of milky?”

“That’s right,” Dr. Luthor says. “It’s water with a little cream added to it, which will help make the demonstration a little easier for all of us to see.”

She moves behind the table and Kara has a clearer view of the setup. 

“Notice that the green diode laser is shining through our cylinder and hitting the wall beyond. Right now, I’ve got a stopper to keep the water in the cylinder, but I’m going to remove it in a moment. Before I do that though, I’m going to ask you to think. Think about light and water. You can think about any iteration of that combination. Imagine a trip to the beach - the ocean and the sun. Imagine a hot tub and its neon lights. Imagine sneaking into the neighborhood pool after dark, with just a flashlight in your hand. Think about the interaction of light and the world of water.” 

Instinct takes over first and Kara thinks about Dr. Luthor and a hot tub. She wonders if Dr. Luthor would wear a bikini or a one-piece, or maybe nothing at all? She lands on a one-piece. She’s got that demure vibe going on, even though her heels have red bottoms. 

With that thought out of the way, Kara closes her eyes and finds herself in the pool, underwater, heart hammering after the gun has sounded and she’s finding the right depth and the right stroke. Her vision is shaded by goggles but sun’s rays pour into the pool. Instead of surfacing, in her imagination she stays underwater, basking in the sunlight and the muted din of cheers from the bleachers and teammates yelling encouragement. 

Dr. Luthor’s voice brings her out of her day-dreaming for a second time in the class. At least this time it was condoned. 

“As we observe the phenomenon of total internal reflection, I want you to try to draw connections between what you’re observing and what you just imagined.”

And then her long fingers are removing the stopper on the cylinder and water begins to flow into the plastic bin below. 

Kara hears a “cool” whispered from the front before she sees it for herself. And then she’s standing, with her back against the back wall as she watches the green diode laser’s light beam through the spout of the water as it cascades into the plastic bin. The laser’s light is no longer shining straight through the cylinder, it’s moving with the water. 

“Cool,” Kara whispers mindlessly. 

Dr. Luthor pulls out a jug of water and pours it into the top of the cylinder to keep the demonstration going. 

“It’s like the light is trapped in the water,” the kid next to her says. Kara nods. 

She doesn’t really participate in the post-demonstration discussion except to turn her head and track each speaker. They might be freshmen, and they might be innocent in the ways of college life, but they’re a pretty smart bunch and Kara finds herself feeling a little intimidated. A few specifically mention science words she’s pretty sure she’s never heard before, which isn’t helping with her confidence.

When the class ends, Dr. Luthor clearly isn’t expecting for Kara to be beside her when she looks up from breaking down the equipment from the demonstration. The room’s gone quiet with the rest of the class having shuffled out.

“I just wanted to apologize again, Dr. Luthor, I feel insanely stupid.” Kara leans against the lab table with her eyes on the equipment rather than on Dr. Luthor.

“It’s quite alright,” she replies, and Kara looks up just in time to catch a shy smile, which she quickly returns. “I’m not much older than a college freshman anyway. I was expecting a few mix-ups, though I wasn’t expecting one at my very first class.”

“How old are you, anyway?” Kara asks without thinking. “I really did believe you were just another student in the class. Now that I think about it, though, I should have known that a college freshman wouldn’t wear a pencil skirt, four-inch heels, and a silk blouse.”

“I might have upgraded my wardrobe just for that reason.” Kara thinks she’s not going to answer her question and then Dr. Luthor leans over the table, closer to her. “Can I let you in on a little secret?”

Kara nods vigorously, eyes meeting Dr. Luthor’s.

“Never ask a woman her age.” Dr. Luthor’s red-painted lips curl into a smile that shows the whites of her teeth and her gums and Kara can’t help but do the same. She had heard Eliza give that same advice a few times before. 

“Well, I’m not a freshman and I’ll volunteer that my age is 21, so we may be closer in age than you think.”

“Oh, you’re the transfer. My colleague mentioned that there would be a junior transfer in this class. Kara Danvers, right? Athlete?” Kara’s heart pounds as Dr. Luthor’s lips wrap around her name. 

“That’s right. That’s also my excuse for being late, but I promise I won’t use that excuse again. And don’t tell my coach I used that excuse or I’ll have to do extra sets at our next lifting session.” She’d already put her foot in her mouth during practice twice and found herself in the gym after hours.

“I doubt I’ll have reason to talk to your coach, don’t worry.”

“Oh no, you’ll talk to one of my coaches at least once every couple of weeks. They check up on us. And if I’m not doing well, they might even sit in on a class. ”

“Really?” Dr. Luthor’s brow furrows and Kara can just make out a vein running along her forehead. “Seems sort of Big Brother, doesn’t it?”

“I guess when the college pays your tuition, they take a few liberties with your liberty, so to speak.”

Dr. Luthor shakes her head, clearly unaccustomed to the level of ownership universities hold over their student-athletes. 

“Well, never fear, I only have good things to say so far, Ms. Danvers.”

Kara tucks her bottom lip between her teeth and looks up at Dr. Luthor through her glasses. 

“Well. I’m working on being late to my next class so I should go. I look forward to the next class.”

“Me too. Nice to meet you Kara.”

“You too, Dr. Luthor.”

Kara swings her bookbag over a shoulder and is almost through the door when she hears, “Oh, Kara, 22.”

“Twenty-two what?” Kara asks, hand clutched against the door’s trim. 

“My age.”

“What?” Kara starts to drift back into the room. “How? Isn’t college...doesn’t it take like five years to get your…”

“Some other time, Kara. Go to your next class.” 

Kara stares a moment longer. 

“Go,” Dr. Luthor says with a wave of her hand and a laugh that Kara tries to memorize.

\-- 

“Lena. How was your first day of classes? Everything you dreamed?”

Lena doesn’t spend much time in her office, at least not so far, but she can’t avoid a trip to the administrative wing that holds each of the science professors’ tiny offices. She’d decided to bring the laser and the other equipment from the demonstration back to her office for safekeeping and figured that her office was as good a place as any to spend a few quiet hours reading the latest study on quantum entanglement. 

Which is how she finds herself instead talking to Dr. Maxwell Lord, campus demigod and star of NCU’s Department of Physics. So much for catching up on that study. Her heels are kicked off under her desk, but she’s sure everything else is prim and proper, so she stays in her desk chair and makes Lord come to her. 

“The day went quite well, Dr. Lord.”

“Truly? Few professors dream of that part of the job.We teach to keep parents’ bank accounts open so that we can play with our toys in the labs when their kids leave on break. Keep your head down and keep those parents happy, Lena.” He gives her a conspiratorial wink that she can’t ever imagine returning. 

“Of course, Dr. Lord.”

“I wasn’t sure if you’d know the way of academia, you’re so young.” He hesitates and Lena wonders if he’s about to comment further on her age, but what comes next is instead much worse than a comment on her age. “But then your brother Lex has quite a reputation in academia, doesn’t he? You’ve surely learned a few lessons from him?” 

Her face heats up at the mention of Lex. Stripped of tenure at his last job and essentially exiled from the field just as she was finishing her Ph.D. program. She’d done her best to distance herself during job interviews, but sharing the Luthor name was a burden she’d realized long ago she would have to shoulder. 

She glances at the clock, then closes the journal on her desk and shuffles a few papers around. “I’m sorry, Dr. Lord. I really should be going. It’s been a long day.”

“Of course, Lena. We should get a drink some time. I’ll take you out for a cocktail and give you some tips on how to pull in those grant dollars. The university will never say it outright, but that certainly factors in to their decisions on tenure”

“Sure,” she replies. She might be ashamed of Lex now, but he had taught her his best tricks for fleeing unwanted attention. Call it a Luthor speciality. Except Lex had somehow found the spotlight and then the spotlight found his transgressions. Well, Lena had always been the smarter of the two. 

\--

She shouldn’t. She knows she shouldn’t. It’s not even that she knows deep down that she shouldn’t, because yes, she knows deep down, but she also knows right here on the surface that  _ she shouldn’t _ . It’s just such a bad idea. What if someone sees her? What if  _ she  _ sees her? What will she say? “Oh, I saw that your swim team is really good and then looked you up online and found out that you’re actually an Olympic qualifier and I just had to check out your first meet.”

There’s no way Kara can see her. She’s never been to the Aquatics Center because _ew_ _exercise_ but she’d seen a picture of it before, in some campus brochure or something. It’s huge. She’ll be fine. There are hundreds of seats here and the pool is so far away. She’s not even sure she’ll be able to make out Kara from up here. She shouldn’t be here, but she’ll be fine.

And then there’s a pair of long tan legs. Muscular thighs. Broad shoulders. Strong, tight shoulders that she could sink her teeth into. 

She knows it’s Kara, even with her swim cap and her goggles on. Her arms swing and dangle and swing again in some weird swimmers’ ritual she’s seen replayed by other swimmers over and over again as she waits for Kara to race.

Aside from the novelty of the first race, most of the other races sans Kara have not kept her attention. The bleachers sit across from massive floor-to-ceiling windows and she starts to imagine a trip the Luthor family took to St. John when she was a kid. Their villa was far above the sea, but the perfect height to catch the sun’s rays hitting the ocean’s waves. In this humdrum indoor aquatic center, in the middle of this humdrum campus, in the middle of this humdrum city, sunlight catches the unnatural cyan water of the pool and transports her. That trip, like so many Luthor trips, was rife with familial tension, but she found her escape sitting on the back patio watching the sun glitter on the sea.

About 25 minutes into the meet, she sees Kara move toward the short platform that almost all of the races seem to be starting from. She looks like she’s lining up for the center lane and Lena wishes she’d brought binoculars. A couple near her have a pair out, though they also seem to be someone’s parents so they are certainly not using them to perv on any of the swimmers the way that Lena might.

When the gun sounds, Kara’s long body seems suspended in the air for a moment before she’s underwater. She’s under for a long time but when her head breaks the surface, the sun glitters in Kara’s wake. She beams through the water, bending with it. 

Somewhere after Kara’s first turn, it strikes Lena that she’s not sure how she’s going to keep talking about the interaction of light with the world without thinking of this very moment. There are lots of different languages that can be used to explain the way that the world works, but this language seems foreign to her, beautiful, dangerous. 

Kara wins easily, flipping her googles up as soon as she touches the wall and her head bobs out of the water. Her mouth drops open as she looks up at the digital display tracking times and then her open mouth angles into a wide smile and she slaps the water. 

When Kara emerges from the pool, Lena feels like a cartoon character that needs to fan herself. Kara swims to the edge of the pool and hoists herself up with those strong shoulders and a laugh that echoes up to the rafters where Lena’s sitting. 

It’s the same pattern for Kara’s three other races, too. Wired on the sidelines. Graceful through the water. Jubilant in victory. 

Lena leaves with several other early exiters, after it’s clear that the meet is winding down. On the way out, she grabs a refrigerator magnet souvenir that catches her eye. It’s the swim team schedule with Kara’s face and upper body prominent in the top right corner. 

\--

It might be the first course she’s ever taught, but Lena thinks she’s found a successful pattern of instruction. Wednesdays are demonstration days and the other two classes of the week are theory, discussion, and some math. Not too much math, she wants to try to keep it light. It is a freshman seminar, after all. 

And, as much as she might roll her eyes at the unwanted advice of Dr. Lord, he’s right that she really just wants to keep parents happy enough that she’ll have the funding to do her research when she’s not teaching. She didn’t take this job to be a teacher. A light class equals happy, interested students equals good grades equals happy parents.

At their first class after Kara’s swim meet, things feel weird. Lena thinks that Kara knows. Her blue eyes seem to always be on her. They’re on her as she turns around from the whiteboard after explaining theory. They’re on her (though they shouldn’t be) as she plays a short video clip to prompt discussion. They’re on her for far too long after she asks a question and looks around the room for an answer. Or maybe, in that last instance, it’s the opposite. That her eyes are on Kara’s for far too long. 

The other two classes of the week pass in much the same way, leaving Lena feeling completely out of sorts. Kara doesn’t say a word in class and doesn’t stay after class. She’s usually out the door before Lena has the chance to take one last look. 

Their first homework assignment is due on the second Friday of class. As soon as she’s settled into her couch that evening, laptop in lap, glass of wine in hand, Lena scrolls through the submissions to find Kara’s paper. The notes that Kara’s been scribbling in her notebook must be solid enough, because the ideas in the paper are B material. The writing, though, has her reading it for a second and then a third time. It’s clear that Kara’s not a science major. The writing is too good. 

Another week passes, much the same. Kara’s next assignment is veering more into solid C territory, Though the writing sometimes distracts Lena, ultimately it’s clear that Kara’s grasp on the concepts from the last week is shaky. She pulls up her email and hits the “Compose” button. Then her hands freeze and her eyes close. She wonders if she would be doing this for that pimply-faced kid who usually sits next to Kara, or if she would be doing this for that girl that just can’t stop raising her hand even after Lena tells her to just talk and not wait to be called on. And then, as much as she doesn’t want to, she hears Lord’s voice in her head saying “Keep those parents happy, Lena.” 

She types in Kara’s email address and suggests she stop by office hours next week to discuss the assignment. After that, she finds herself checking and rechecking her email, wondering if Kara might respond. When she goes to the fridge for a second glass of wine, she sees it: there’s another meet tomorrow. Lena weighs her options for about 30 seconds before she decides that it’ll be fine. It was fine the first time, it’ll be fine this time, too.

She convinces herself that her interest is about the water and the light. 


	2. Prism Rainbow

There’s a soft knock at her office door and when Lena looks up she realizes that her office hours started 30 minutes ago. 

She sets her feet back into the heels she usually kicks off under her desk, then stands and wipes her hands down the front of her slacks, smoothing out the wrinkles. Then, she’s across the room in three strides and propping the heavy wooden door open.

Kara’s blue eyes are the first thing she sees. Then the whites of her teeth. It’s that 1,000 watt smile she’d seen at the Aquatic Center after each of her races. This smile hasn’t shown itself in class, but she’s glad to see it greet her for the first time here. 

“Hi Dr. Luthor. I hope I’m not bothering you.”

“No please, Kara,” Lena says, stepping aside and showing her in. “I suggested you come by to see me during my office hours, you’re meant to bother me. Please, have a seat.”

She pauses for a moment at the door. 

Closing it would mean that their conversation would be uninterrupted. Keeping it open would show that there’s absolutely nothing secretive going on inside. Closing it would mean that she could lean into this niggling personal curiosity that she has about Kara, even if for just a few minutes. 

She keeps the door open.

“Right. Of course. I did want to apologize again,” Kara says a little timidly, watching Lena sit back down behind her desk. Lena keeps her heels on this time. “I still feel weird about what happened.”

“Kara, you really don’t have to apologize. Consider it forgotten.”

“I don’t think in a million years that I could forget it,” That big smile is back and somehow brighter than before and it’s hard for Lena not to smile when she sees it, even if the smile is that toothy open-mouthed one her mother used to chide her for. “That’s going to be a story I tell my grandchildren. Everything from the part where I was dripping sweat on the classroom floor to the part where I stared deeply into your eyes and dropped the most perfect pickup line ever to the part where that laser moved through the water like that.”

_ The most perfect pickup line ever _ . Of course she remembers what Kara said, but somehow, in the delirium of the first day of classes the exact words of it had fallen into the back of her mind. Had a freshman boy uttered those words, Lena no doubt would have immediately reprimanded him. Instead, she’s sitting across her desk from the person who uttered them - at her invitation. 

“You know, I probably won’t ever forget it either. But there’s no need to keep apologizing. Apology accepted. Let’s move on.” 

“Right. Ok. Thank you.” Kara leans over her desk, placing her notebook atop it. Lena catches among the flipped pages a couple doodles and some familiar symbols for physical quantities that she’d introduced at the last class. “Anyway, about last week’s assignment. I’m a journalism major, so I’m not really a physics person, though you probably knew that…”

“Nonsense,” Lena interrupts. “No one is born a physics person or ‘not a physics person.’” 

Kara looks up with something like a gleam in her eye. “I think you were probably born a physics person.” 

“Maybe you’re right.” 

In the Luthor household, an open-mouthed smile was rarest of all. It was the ultimate form of vulnerability. The tight-lipped, grimacing smile was far more frequent. Around Kara, Lena can’t help but bare the pinks of her gums and the whites of her teeth after so many of the things she says. “Well, I hope I can help you feel a little bit more like a physics person. Let's talk about last week’s assignment.”

Kara’s never really participated in class beyond the occasional question, so office hours feel like something revelatory to Lena, in many ways. Most importantly (or most professionally), it’s clear that Kara’s right, she’s not much of a physics person. But it seems that’s true mostly because she doesn’t have a very good physics foundation. 

When she can set aside her professionalism (she shouldn’t, but she does), Lena also finds Kara herself to be revelatory. She’s clever and funny and curious. She’s an attentive listener. She’s more modest and self-reflective than Lena had thought she could be for a star athlete who hits on her professor the first day of classes. This side of Kara, really this collegiality and easy conversation, has her longing for something she’s never really had.

“If you don’t mind me asking, Dr. Luthor, how are you a professor at 22? Some days I feel like I can barely manage to put my shoes on the right feet.”

“It’s been a bit of a lonely path, if I can be honest.” She could say more, but she doesn’t want to. Somehow, Kara’s bright eyes and thoughtful silences have pulled this much out of her, far more than she’s shared with anyone aside from Sam in quite a while. Rather than let the moment hang in limbo, she immediately follows with: “You don’t give yourself enough credit, Kara. You’re an accomplished athlete and a good student. That’s a difficult balancing act you’re managing.”

Kara doesn’t respond right away, seeming to be stuck for a moment at Lena’s candor. But, she also seems to be perceptive enough to move on rather than linger. “Aw shucks, Dr. Luthor. How do you know I’m an accomplished athlete and a good student, anyway?”

Lena feels caught at the ‘accomplished athlete’ line that’s been turned around on her. “Call it intuition.”

“Well, I hope I can prove you right, about the good student part, at least. I already know I’m an accomplished athlete.”

“And humble.” There’s this flutter at the cadence of their conversation and how easily it moves. It’s foreign and thrilling. 

“The humblest,” Kara says with a laugh that Lena soon joins.

Then, there’s one of those awkward moments where the laugh has ended and smiles are fading and they’re just looking at each other and then quickly looking away. Kara’s cheeks go pink and her eyes soften and she licks her lips and Lena captures it all in her mind and stores it away for later. 

“I’ll be honest,” Kara starts, voice lowering and leaning back toward Lena’s desk. Lena’s heart picks up, contemplating where the start of this sentence could possibly go. “I really didn’t want to take this class. There was a class called Journeys through Hell I saw in the course catalogue. How cool would that class have been?”

“Get your Ph.D. and every class you take will be a Journey through Hell.” And then they’re laughing again and the awkward moment drifts away. 

“By the time I was ready to sign up for a seminar, my choices were Fashion through the Ages, Russian for Dummies, and your class.”

“Tough choice.”

“The Interaction of LIght with the World. I signed up for it before I even read the course description,” Her voice is suddenly serious. “Just took a leap. But the title of your course is beautiful, you know?”

Lena’s tongue feels heavy in her mouth.

“Physics explains all the beauty that the eye can see and much more that it can’t,” she replies, voice a little shaky.

“I’m learning that,” Kara says, eyes locked onto Lena’s.

_ Knock knock _

The sound jolts her and she’s instantly grateful that she didn’t close the door. 

“Dr Luthor...oh, sorry, I didn’t realize someone else was here.” 

“No please, come in, we were just wrapping up. You’re here for office hours, I assume?” She hears Kara shuffling, putting her notebook in her bookbag, stuffing a pencil back in the front pocket.

“Yes.”

“Very well. Kara,” she says with one last appraisal until their next class, “thank you for stopping by.”

“Thanks for your help, Dr. Luthor.”

\--

Kara’s in her usual seat come Monday morning. There had been no meet this weekend according to her magnetized swim team schedule, which Lena assumes to mean that Kara had a weekend of two-a-day practices, some studying, and plenty of social activity. She imagines Kara at a fraternity party, dressed in a bedsheet toga and chugging beer out of a solo cup and the idea doesn’t completely repulse her. At least it doesn’t repulse her as much as it might have during her own time in college. After her second thought of Kara in a toga, she tries to wipe the image clean out of her head lest she get any deeper than she already is.

“Good Monday morning, everyone. Let’s get started, shall we? For the next week, we’ll be examining refraction. Refraction is the change in direction of a wave passing from one medium to another caused by its change in speed. Today, we’ll review the phenomenon in more depth and discuss the mathematics of refraction. On Wednesday, as always, we’ll do our demonstration, and on Friday we’ll focus on discussion, application, and questions.”

There are the idle sounds of notebook pages flipped and pencils quietly scraping across paper as Lena moves around the table to the whiteboard. This is a frequent occurrence on Mondays - her back to the class, scrawling on the whiteboard. She’d been a bit self-conscious about it at first, never fully turning her back for fear that something nefarious, or just embarrassing might be happening behind her, but after several weeks of absolutely nothing unsavory happening, she’d eased into this new level of comfort.

Today, she’s carefully selected a pair of high-waisted, wide-legged black pants and a crisp white tucked shirt with a few buttons tastefully undone. Her hair is in a standard, sleek high ponytail. She’d had this outfit in mind since last week. She’d even tried it on and sent a mirror selfie to Sam for her opinion, which is how she’s come to wearing a chunky black heel instead of a stiletto. She could always count on Sam’s solid fashion advice.

On typical Monday mornings, she starts with a basic formula. Today, instead, Lena writes on the board:  _ “...he destroyed the poetry of the rainbow by reducing it to a prism. _ ”

When she turns around, she finds Kara’s eyes wide. Lena had been looking for this quote all weekend. It had been buried somewhere in the back of her mind since the beginning of grad school and she’d scoured notes, old textbooks, and the internet until she eventually found it. 

“On the first day of class, I mentioned that there are lots of different languages that explain the way that the world works. One of those ways is math, as we’ve learned in classes since. But poetry, literature - the written word - is another. I don’t want us to lose sight of the different languages we can use to describe the phenomena we talk about in this class.”

She tries to avoid Kara’s eyes as she talks, fearful that they might distract. But between these longer pauses, she briefly takes in Kara’s reaction. Her eyes soften and catch one more time on Lena’s before she’s scribbling something in her notebook. 

“This is a quote from the poet John Keats. The ‘ _ he’  _ in this sentence is Isaac Newton. At Friday’s class, we’ll return to this quote and discuss its merit given the learnings of the week. Make sure you write it down, please.”

The rest of the class is similar to any other Monday class. Mostly, Lena talks, her voice echoing off of the whiteboard, while she scrawls symbols and equations across it. Occasionally, she reminds herself to turn around and ask whether there are any questions. There often are. 

At the end of every other class except the first, Kara had left without saying a word or even a glance back at her, but today she lingers, slowly packing her bookbag. 

When Lena finishes answering a question from another student, she finds Kara standing at the front of the room, waiting for her. 

“Dr. Luthor, thank you. Today’s the first day I felt like a physics person.”

“You don’t know how happy I am to hear that, Kara.”

“I look forward to Wednesday’s demonstration and Friday’s discussion.”

“And I look forward to your contributions.”

“Ok, well, bye Dr. Luthor.”

“Bye, Kara.”

\--

A blip in her weekly schedule means that she has to hold office hours on Tuesday instead of Thursday. The change in routine means that when Kara drops by, her hair smells like chlorine and her eyes are tired behind her glasses.

“Hi Dr. L.” She still greets Lena with that 1,000 watt smile when she pops her head in the door. 

“Kara. It’s nice to see you,” Lena says, standing at her desk and waving Kara in.

“Really?”

“Of course,” Lena laughs.

Kara takes a seat and pulls out her notebook to rest on Lena’s desk. “I just wanted to ask you a couple questions to make sure I’m understanding refraction and the math you taught us yesterday.”

“Anything.” 

“Don’t say that or you’ll find me in here far more often than you’d want.”

“I doubt that.”

Kara hesitates, studies her for a moment, and then begins: “So here’s my first question…”

After two of these office hours meetings with Kara, Lena notices a trend. When Kara talks about physics, Lena finds that for the most part she can slip out of this unmoored persona she’s found herself in lately when Kara is near and slip into a persona that’s far more professorial. The persona that she should always be in whether she’s near Kara or not, at least on campus. 

Kara scribbles more notes in that blue composition notebook she pulls out at the beginning of every class and by the end of their question-and-answer session, Lena’s pretty sure Kara’s in B+ territory for the next assignment. When she closes the notebook and shoves it back into her bookbag, Lena finds her professorial persona slipping again. 

“You know,” Kara starts, still firmly seated in the chair on the other side of Lena’s desk, “you’re a really sharp dresser for a 22-year old associate professor. You must have really updated your wardrobe becauseI don’t think I’ve seen anything repeated yet..” Somehow, Kara never fails to mention her age in these postscript conversations.

“I don’t think that’s true.” Lena looks down at today’s outfit, a sheath dress color-blocked with pastels above the waist and a black bottom. “I’ve worn the floral-patterned silk shirt and pencil skirt combination more than once.” She leaves out mention that it’s a  _ Gucci  _ floral-patterned silk shirt. Kara doesn’t need to know about Luthor money, not yet or maybe not ever. 

“Was that the outfit you wore on the first day?”

“I think so.”

“No, I would have remembered that.”

It is Lena’s favorite combination so far, which is probably why she thinks she’s worn it more frequently. Maybe she has, just not in Kara’s presence. She decides then and there that it should make a repeat appearance in class soon.

“You’re a sharp dresser when you want to be, too,” Lena replies a little too quickly. “That blue oxford cut quite the look on you the other day.” It was one of those rare days that Kara hadn’t arrived in a sweatsuit with a school logo emblazoned on it. She’d imagined Kara carefully selecting it from her closet, checking herself out in the mirror, tucking it in and then untucking it. 

“I didn’t know you were paying attention, Dr. Luthor,” Kara says, voice going a little deeper and a little more playful.

“A sharp dresser like me recognizes another sharp dresser when she sees one.” 

Lena’s phone dings from atop her desk. At the break in conversation, Kara glances at the clock on the wall.

“Looks like office hours was up 20 minutes ago, sorry about that. I don’t want to keep you.” She doesn’t move, just looks to Lena.

“Oh, you’re right. I need to get moving. I’ve got to take a couple trips to my car to haul all of this equipment back to department storage before they lock up for the night.” Lena had just received her first minor reprimand from the department’s administrative assistant about hoarding some of the equipment she’d been using in her demonstrations. Out of all of his unsolicited lessons in academia that he’d given to Lena, one of Lex’s better ones had been about the importance of the ‘help.’ She’d chided him on using that term, obviously, but the lesson remained--some of the most important people in her professional success would be people like the department’s administrative assistant. Though it was tempting to delay for another day, especially with Kara looking so eager in her presence, she’d convinced herself that this menial task of equipment return could have major career implications. 

“Let me help. It’ll save you a trip.” Kara’s moving before Lena can say anything, finding the boxes against the wall. 

Practicality wins out over momentary hesitance. Two trips versus one? In heels and a dress? 

“Ok,” she says, throwing her trench coat on. “Do you mind getting the heavy box?”

“That’s what these are for.” Kara flexes and kisses a bicep through the sleeve of her swim team shirt. 

The walk to the parking lot is silent. Kara is in front of her, blazing a path and if Lena were a complete idiot, she’d have her eyes on the way Kara carries a 60-pound box with ease. But she’s not a complete idiot and she’s trailing Kara so that she can keep one heeled foot in front of the other, lest she break an ankle. When Kara gets too far ahead, she stops and looks back at Lena until Lena can catch up and the pattern repeats.

Lena catches up to Kara in the parking lot and then it’s her turn to take the lead. “Come on, muscles. I’m parked this way.”

“I thought for sure I’d be lugging this stuff into the trunk of a Beemer, Dr. Luthor,” Kara says when they get to the car.

“Just your standard Prius, I’m afraid.” She sets her box down as easily as she can in a sheath dress and heels. Once both boxes are in the trunk and the trunk is closed, there’s another one of those awkward pauses where they’re just standing there, looking at each other for a moment. 

“Kara,” Lena starts. She hears emotion in her voice come unbidden and pauses to tamp it down, “the age thing has been bugging me lately.”

Kara’s brow furrows. “What do you mean? Like how young you are to be a professor? It shouldn’t bug you, it’s a tremendous accomplishment.”

“Thanks, but, I don’t think it’s that,” Lena looks down and shakes her head. “It’s the age difference between us. Those freshmen in the class feel like they’re a whole generation younger than me. But you…”

“When’s your birthday?”

“The beginning of August.”

Kara laughs. “We’re not even a whole year apart. I’ll be 22 at the end of December.”

Hearing that somehow makes it better. It’s not. Nothing has changed. But something in Lena feels lifted after Kara says it.

“Do you think...can you call me Lena instead of Dr. Luthor - not during class or when other students or professors are around, but maybe when it’s just us, like it is now?” She looks away, ready for Kara to reject her request and using one of those old tricks to protect her heart. “For so much of my life, I’ve been isolated from my peers. Mostly, I hadn’t really known what I was missing, but talking to you lately has made me realize that I’ve missed a lot.”

Kara looks at her in silence for long enough that she’s glad she’s looking away. She can’t bear to meet her eyes. 

“I’m sorry, Dr...Lena,” Kara’s not whispering but her voice sounds quiet, intimate. “I’ve definitely known that feeling, though maybe not as...intensely. I’m glad to be your peer, and maybe your friend, too? Secret friend?” 

Kara holds out her hand and when it falls into Lena’s line of sight she looks up to find Kara smiling. Lena shakes it and laughs.

“Secret friend,” she whispers, holding onto Kara’s warm, soft hand just a moment longer. She’d thought it might be calloused, given Kara’s weight-lifting regimen, but four hours daily in the pool must wash that wear away. 

“I think we’ll be safe on a first name basis as long as it’s just the two of us.”

“Right-o. Lena. Very cool.” Kara’s smile is tinged with a blush, her head bent down though she looks up at Lena through her glasses. 

“Cool indeed.”

“Well…” Kara hesitates. Lena thinks she might be coming in for a hug. Kara seems like the type that would hug a friend in this moment, especially after Lena’s emotional reveal. Lena finds herself contemplating it, too, but the contemplation lasts so long that everything just feels weird instead.

“Well ok,” Kara begins again, “I’ll see you in class. Lena.”

“See you then, Kara.”

\--

“Today’s demonstration is called the Prism Rainbow. It’s going to be one or our simplest demonstrations and one of our most interactive. Rather than demonstrating the prism rainbow at the front of the room, today I’ve brought one of these for each of you.” She holds up a small glass prism. “And we’re lucky enough to have ample sunlight today for our demonstration.

When you get your prism, you’ll have about 10 minutes to explore the ways in which the light interacts with the prism. Log observations and questions. If you’re feeling today like a Keats instead of a Newton, be poetic in your observations. If you’re feeling like more of a Newton than a Keats, try to apply some of the mathematical concepts we learned on Monday. Feel free to remain in the class or take it out into the hallway.”

Kara follows the class’s makeshift line to the front of the room to pick up a prism. When she reaches the box, her eyes flick up and meet Lena’s for a moment before she turns away. When Lena looks up again, Kara’s gone. 

In the final two minutes, she finds Kara at the end of the hall by herself. A couple of students are at the other end of the hall, where the light is dimmer, no doubt observing the prism in a lower light. 

“Are you here to help me unweave a rainbow?” Kara asks as she approaches. 

Lena leans her side against the wall, crossing her arms and watching Kara twist the prism this way and that in the sunlight. “If the sun’s light consisted of but one source of rays, there would be but one color in the whole world.”

Kara’s eyes narrow and look up at that. “That’s not Keats, right?”

“Newton.”

Kara smiles. “It shouldn’t be a surprise that I’m quoting Keats and you’re quoting Newton.”

“No surprise at all,” Lena says, leaning the side of her head up against the wall now, too. “Tell me what you see?”

“Well. I see ROYGBIV.” 

Kara looks up, as if to weigh her answer against Lena’s expression. Lena nods. 

“And that’s because of refraction.” Her eyebrows wriggle at Lena. 

“That’s not your observation, Kara. That’s a conclusion that you’re drawing. Just say what you see.”

“Um,” she gets serious again, and maybe a little apprehensive, too. “The colors of the rainbow always show up in the same sequence.”

“That’s something.”

“A third grader could make that observation.”

"I’m not expecting anyone in this class to surprise me with their observations, Kara. You’re just talking about what you see.”

“I see something beautiful.” Kara’s eyes look right at her and Lena finds herself breathing in and breathing in until she has to remember to exhale. 

Lena pushes off the wall and steps closer to where Kara’s rainbow is displayed against a blank page in her notebook on the window’s ledge. Their backs face the hallway and their heads are so close together that they can whisper. 

“Do you want to know something interesting?” Lena asks. Their faces are so close that she can see her face reflecting off of Kara’s glasses at the right angle. “Each of these colors is a different temperature.”

Kara tears her eyes from Lena’s and looks down at the paper, moving a longer finger through the prism’s light. 

“It’s too subtle, you won’t feel it,” Lena continues, “but the red band is the warmest light we can see.” Kara’s finger moves over to the reddest part of the prism rainbow. 

Lena’s arm then crosses over Kara’s and rests a finger just next to hers. “Just beyond the red band is the highest temperature. There’s light there too,” she says, eyes tracing over Kara’s hand, “but it’s a lower frequency than we can see.” 

Kara's finger moves to touch Lena’s. 

As Lena looks up toward Kara, her phone chirps and buzzes in her pocket and she steps back suddenly. “The time,” she starts, digging her hand frantically into her pocket to silence it, “time is up. We should go back.”

Lena’s glad that she wrote down the guiding questions for the post-observation discussion or she’s positive she would have sat in stunned silence for the next twenty minutes of class. The other students don’t seem to notice any difference, but Kara certainly does. Her eyes catch Kara’s once at the beginning of the discussion and she knows she can’t look up at her again without something dreadful (or wonderful) happening. 

\--

The next couple of classes pass with no further interaction with Kara and it’s almost as if it didn’t happen. Lena still tries to avoid meeting Kara’s eyes and it seems that Kara might be trying to do the same. And then, after the next demonstration class on Wednesday, Kara bounds up to the front of the room and asks a question about the connection between the demonstration and the theory from Monday’s class and then bounds away again. 

The prism rainbow experience is all but forgotten, it seems. Until it isn’t.

At Thursday’s office hours, Kara’s head pops in Lena’s doorway. 

“Lena?” 

“You know, I thought an accomplished athlete and good student like yourself might have better things to do than hang around during my office hours each week.” Lena leans back in her chair as Kara leans in the doorway, arms crossed in a way that Lena thinks must be on purpose to show off her biceps, or her forearms, or both. 

“Maybe this is a part of being a ‘good student’? Though given my performance in your class, I don’t know where you’re getting that characterization from.”

“Ingratiating yourself to your professor can only help in bending the grading curve in your favor.”

“You miss 100% of the shots you don’t take.”

“That sounds dangerously close to a sports adage.” Lena’s not really sports-averse, just sports-dumb, maybe? The only purpose sports have served is as an excuse to watch beautiful bodies at work.

“If you can talk physics to me, I need to be able to talk sports to you. Capisce?”

“Indeed. So how can I talk physics to you today, Kara?”

“So this prism rainbow.”

“Come in. Close the door.”

There’s a soft click as the door closes and the buzz from the hallway disappears. 

“I saw you had one on your desk the other day.”

“It doubles nicely as a paperweight. Now that the sun is setting earlier, the light is just right at this time of day.”

Lena fiddles with it, moving it around in the light until a rainbow bursts across the center of her desk. 

“Let’s see how much I remember: there’s the spectrum of light. ROYGBIV and all of that. Violet has the shortest wavelength,” Kara says. She’s leaned forward and Lena can see a fleck of hazel in her eyes as they meet hers. 

She nods and Kara continues, “And red has the longest wavelength. 600 nanometers?”

“650,” Lena corrects, voice quiet. 

“Beyond the red band, there’s infrared, which we can’t see.”

Lena nods again, but Kara’s stopped talking and is just looking back at her.

“Do you think...is there any way I can see you outside of class? And office hours?” 

Kara’s hand moves from the edge of her desk and it looks like she’s about to reach across to Lena.

“I’m not…”

“I mean,” Kara interjects before Lena can reflexively turn her down, “it doesn’t have to be anything you don’t want it to be. As friends?”

“I don’t...I don’t know, Kara.” She’s been thinking about this moment. Hoping for it. But she hasn’t played it out past this point and it’s throwing her off balance. “I enjoy your company. That much is obvious, I think.”

Kara senses Lena’s hesitation and adds: “It could just be meeting up for a coffee or something. Professors and their students do that.”

“Let me think about it, ok?”

The moment she’s been thinking about has now happened and even in her bumbling, she’s bought herself some time to figure out what’s next. But that doesn’t make her decision about what happens next any easier. Kara’s hopeful look lingers in her mind for days.

\--

A week later, Kara’s proposition is all she’s been thinking about, but she still hasn’t given her an answer. 

Then an email pops into her inbox. 

_ Friday at 5:42 a.m. _

_ Dr. L -  _

_ I write to you a battle-weary, amphibious soldier trekking into combat once more. When the dawn of ‘morrow breaks, our foes will be upon us. As you might have surmised, I shall be absent from your presence today and all of the days until Monday’s morn. On that day, our regiment has been granted by the general a day of rest. Perchance we meet at Ye Olde Noonan’s Shoppe so that I might be schooled in the ways of your dastardly science? _

_ Should I perish in these days to come, find me in the light that breaks across each day’s horizon. _

_ Yours,  _

  * _K.D._



She reads it three more times immediately after she’s read it the first. When she finishes her shower, she pulls it up as she sits at the edge of her bed in a towel and reads it again. After she’s reviewed the day’s lecture notes over coffee at the counter, she reads it again. She’s about to forward it to Sam because she so desperately wants to talk to someone about whatever the hell this is, but everytime she hovers over the “Send” button, she thinks better of it. This note feels too private and their budding...something...feels too fresh to talk about, even to her best friend. 

When she hits “Reply,” she’s wracked with just as much torment. She’s so taken with this note and she wants to put a modicum of effort into the response, given Kara’s careful wording. But she’s also responding from her official university email address, Lex’s indiscretions are wreaking havoc on her psyche, and Dr. Lord’s reminders keep coming back to her.

She quickly types out a response and hits send.

_ Friday at 7:59 a.m. _

_ Kara - I think this is your clever way of asking me if I can help you catch up on what you’ll miss at today’s class. I’ll meet you at Noonan’s 30 minutes before Monday’s class. Good luck at your meet. - Dr. L. _

\--

Noonan’s is tucked away in the basement of the Clark building and Lena finds Kara seated at a table in the corner. Her hair is pulled into a loose braid and she’s wearing a light navy cardigan over a patterned button-up shirt, unusual for Kara’s Monday morning attire. 

“Dr. L., thank you so much for agreeing to meet.”

“My pleasure, Kara. Can I get you a coffee?”

“No please, I invited you, so it’s on me. What would you like?”

Lena’s reviewing Friday’s notes at their table when Kara returns with a full tray. Three drinks, a croissant, two muffins, and a donut threaten to spill over as Kara sets the tray down on their tiny table. 

“Are we feeding your regiment this morning, soldier?”

Kara rubs her hand nervously against the back of her neck. “I wasn’t sure if you were hungry.”

“I don’t really eat breakfast.”

Kara’s eyes go wide and she leans across the table, shirt almost catching the top of one of the muffins. “Lena! Shoot...I mean, Dr. Luthor! You have to eat breakfast.”

“I’ve done fine without it for the last decade. I’ll survive.”

Kara stares at her, aghast. 

“Well then I hope you don’t mind if I help myself.”

“By all means.”

“So,” Kara begins, after she’s chewed enough of a huge bite of croissant that she can talk again. Lena can feel her face twist into something between horror and amusement. “What’s the most important stuff I need to know?”

Lena opens her notebook and turns it around so that her scrawling notes face Kara. 

“You write like a doctor.”

“I  _ am  _ a doctor.”

“Ahh, got me. I meant…”

“I know what you meant, jerk.” She laughs and then starts pointing at her notes, reading them upside down, and explaining them to Kara. That crinkle in Kara’s brow that Lena sometimes wants to reach out and soothe pops up just before she has a question and Lena can’t help but look up at Kara occasionally to see if the crinkle’s coming. 

“That took less time than I thought it would,” Kara says when they’re done ten minutes later.

“Are you feeling caught up?”

“I am. No more questions. Well maybe one more question: did you have a good weekend?”

“I...did. I…” Her weekend had been like any other: grading assignments, preparing lecture notes, reading the latest research, writing grant applications. It seems terribly boring in comparison. “How did your meet go?” she asks instead of supplying an answer.

“My regiment is always victorious in battle. You should come see us sometime. We have a couple meets coming up.” There’s a tiny bit of relief that Lena feels in finding that Kara has no idea she’s already been to two of her meets. 

“I’ll check my calendar. Class starts soon, we should get moving.”

She packs in a hurry while Kara tosses their trash and starts toward the door.

“Lena,” a familiar voice calls as she starts to follow Kara. “I don’t usually see you here this early.” Dr. Lord is looking up at her from his table. 

Kara’s back was to him while they were at their table, but Lena should have seen him sitting here. She was facing him. Though she wasn’t exactly paying attention to anything but Kara in the last thirty minutes. She’s not sure if knowing that Dr. Lord were here would have changed anything about her demeanor toward Kara, but the fact that she’s thinking about it has her flustered. 

“Oh, Dr. Lord. Just getting a coffee before my Monday class.” Kara’s back at her side and she sees Lord’s eyes appraising Kara. “Go ahead, Ms. Danvers, I’ll meet you in class.”

They both watch Kara leave. 

“Danvers -- the swimmer?”

“The team traveled this weekend and she asked for some help catching up on what she missed in Friday’s class.”

“Well you’ve really taken to the ‘keep the parents happy’ motto, haven’t you? But you don’t need to keep athletes’ parents happy. Student-athletes are indentured servants. Anyway, I’ve been meaning to tell you that I’ve ordered some equipment for the department that’s going to be a game changer. It’s supposed to be delivered just after Thanksgiving. The department offices will be closed, so I’m having it delivered to my house. Would you like a first crack at it before the rest of the department?”

“Oh, uh.” She’s shaken by so many things in that moment: that she’s run into Dr. Lord, that she’s run into Dr. Lord with Kara, that Dr. Lord might have seen them sitting together, that Dr. Lord might have seen her laughing with Kara or smiling at her or that he could somehow hear her heartbeat speed up when Kara would look up at her after writing another note in her notebook. 

“Why don’t you bring it by my place when it comes in?”

She regrets it as soon as she says it. It’s just that he seemed to be setting her up for a ‘my place or yours’ scenario, and at the very least at her place she would be in control. She could greet him at the door and suggest they check it out in the parking lot rather than inside her apartment. 

That might work. 


	3. Laser Gun

**Notes for the Chapter:**

> Tag added: thar be smut ahead.

Lena met Sam Arias at thirteen, in their first year as boarders at Mount Helena, when she was still going by ‘Samantha.’ Just two years later, Lena was on her way to MIT and soon enough on her way to a doctorate. But in those two years, Sam had forged a bond with her stronger than any other person in her life. 

There wasn’t exactly a massive list of people in Lena’s life who’d forged that kind of bond with her, so Sam wasn’t clamoring up the ranks to sit at the top. Seventy-five percent of the reason for that was Lena’s family: devious Lex, cold Lillian, absent Lionel. But the other 25 percent could be blamed on Lena’s own resistance: to proximity, to friendship, to intimacy. Sam had helped her out of some of that. She had also helped her ease into therapy in her last year of working on her doctorate, which helped even more. 

For the first three years of their friendship, Lena had felt like she was the weak one, hanging onto Sam by a thread. She worried Sam would drop her once she noticed just how emotionally frail she actually was beneath the surface. 

And then Ruby came along, with her soft, soft skin and sweet milk-drunk smiles. It was then that Lena realized that friendship wasn’t about strength or weakness, it was about comfort and support and happiness. Sam had offered her those things for so many years, and she found a silent joy in being able to do the same as their friendship progressed. Lena also found an uncharacteristically vocal joy in watching Sam become a doting mother. 

One of the reasons Lena interviewed for the associate professor job at NCU was because Sam was working on her Master’s degree in business there. Though they hadn’t lived in the same place since Mount Helena, they’d probably spent thousands of dollars over the course of their friendship flying cross country to visit one another. 

She’d actually debated whether or not to tell Sam about Kara. Yes, Sam was her very best friend and gave great advice. But, Sam was also relentless in her advice. Once it was delivered, it was to be followed. And Lena knew that Sam would push her to explore whatever it was that might be between them. It terrified her.

It turns out, Lena didn’t need to tell Sam everything. An intimate friendship of nearly a decade means that your friend can guess when something’s up. She’d mentioned Kara’s name in a way that she thought was off-handed a couple times in conversation with Sam and soon, Sam was asking about Kara at their weekly Wednesday Wine Night. One week, it was,  _ How’s that swimmer you mentioned, the one who’s in your freshman seminar?  _ The next week, it was,  _ I looked up that swimmer, Kara Danvers, who you said is in your class. She’s something, Lena. Your type.  _ And then finally, it was,  _ Everytime I mention Kara’s name, you should see your face. Just go for it, Lena.  _ After that, Lena attempted to put the kibosh on it.  _ I can’t, Sam, even if I wanted to. And you’re not exactly helping me take my mind off of her. Nothing can happen. _

And she was resolute about that statement. Until she wasn’t. 

\--

Wednesday’s demonstration had the most complicated set up to date. She’d never done this demo herself, just seen it done, once in person and several times online. Most of the weekend before, she’d spent watching YouTube tutorials and trying to blow up a balloon inside of another balloon, which seemed like the most challenging part of the demonstration, all things considered. 

By Wednesday morning, she carefully carries her nestled balloon creation into the classroom early for set-up. 

The way she’s designed the day’s class means that the first thirty minutes are spent continuing Monday’s lecture, including introducing the Beer-Lambert law, which gets a chuckle and a murmur of “beer” from the 18-year-olds taking notes behind her as she scribbles on the white board. 

When she turns around to take questions, she usually catches a few eyes staring at the demonstration set-up, students’ curiosity warring with their attention-span. 

And when it’s finally time for the demonstration, those with frayed attention are wide-eyed and hungry for it. Kara’s among them. One of the pimply-faced boys who regularly sits next to Kara had asked a question about half-way through the lecture and when Lena had glanced over at Kara hoping to catch her eyes, she’d instead found Kara not scribbling in her notebook, but admiring the red balloon blown up inside the clear balloon. Now, Kara’s half-standing with one leg on the floor and one knee on her seat as she watches Lena move around the demonstration table up front. 

Most of the other students appear to be just as interested. Clearly the prism rainbow demonstration was elementary in comparison to this one. 

Lena eventually does catch Kara’s eyes on her just before she’s about to turn the laser gun on. Her heart does this thing that she’s been trying to ignore and her cheeks and chest heat up under Kara’s gaze. She looks away quickly, worried that other students might somehow be able to tell why she’s suddenly blushing. 

“Pay attention because this is going to be over quickly,” she says to the class. There are a few murmurs at that and another couple of students against the back wall stand up at their desks like Kara.

And then she turns the laser on to beam against the balloons. Within seconds the red balloon pops inside of the clear one, which remains intact.

There are several gasps in the room, which makes Lena laugh a little, if only because she had forgotten that this is novel for so many students in the room. A few others say “Cool!” like they always do for the demonstrations. Kara’s usually one of those people who says it too, but Lena looks over to find her back in her seat, leaning over her notebook and scribbling away. 

“The outer balloon is clear,” she begins, as other students settle back in their seats to take their own notes, “so the laser goes right through it without being absorbed by it. The inner balloon, though, is red, which absorbed the light from the laser, which caused it to heat up and then pop.

This is called selective absorption of light. When the light wave from the laser gun hits the clear balloon, its waves are passed on, or transmitted. The light wave then hits the red balloon and because the light wave hits a material with electrons having the same vibrational frequencies, the electrons absorb the energy of the light wave and transform it into vibrational motion. During the vibration, the electrons interact with neighboring atoms in a way that converts the vibrational energy into thermal energy, which then results in…”

“Pop.”

“That’s right, the red balloon bursts because of that thermal energy.”

Students are still talking about the ‘pop’ when they filter out of class and Lena starts to think that maybe the teaching side of academia isn’t as bad as they make it out to be.

\--

Saturday mornings she usually wakes up early, then leisurely works through her morning routine: coffee, shower, reading, a walk on the trail by her apartment if it’s nice outside. But this morning, everything is off. She wakes up late because she’s forgotten to charge her phone. There’s no coffee because she’d run out Friday morning and had forgotten to stop by the grocery store to pick up some more. She sits down to read a journal article she’d bookmarked and keeps reading the same paragraph over and over again. And it rains and rains. 

So when Sam calls on Saturday afternoon, her mindset is right where it needs to be to be suckered into one of Sam’s schemes. 

“I want to take you out for a night on the town. Help you get your mind off the swimmer. ”

“Who says it’s on her?”

“I know you.”

“I don’t know, Sam. What about Ruby? We could just do something at your place.”

“The babysitter is blessedly free tonight, so we’re going out. C’mon Lena, live a little. You’re 22, not 52.”

“Fine. But it has to be somewhere at least five blocks from campus. I need a little distance from this place.”

“Ok. Yeah. Actually, that fits.”

“What do you mean ‘that fits’?”

“I had this place in mind and it fits with your stipulation.”

“What place?”

“I’ve been kind of talking to this guy who owns a dive bar not far from here. More than five blocks, but still not far. I think he’d probably give us a bunch of free drinks.”

“Well, if I’m going to be dragged out, I might as well do it on the cheap.”

\--

They make a beeline straight to the bar. The place is pretty dingy and Lena assumes that her drink of choice tonight will not be top shelf. She doesn’t get a chance to take in much of the scenery aside from those initial observations, though. Sam’s literally pulling her toward the bar, like Lena might escape if she lets her go. 

Sam keeps her occupied enough through one drink and an awkward conversation with the bartender that she still doesn’t have much of a grip on the place or its clientele as Sam slips to the bathroom and the bartender brings Lena her second drink. Lena takes the time, while Sam is away, to do her due diligence as a friend and make sure this bartender guy isn’t a creep. He seems nice enough, and even Lena can admit that he’s attractive, but when he starts talking about his time at NCU and his extracurriculars she quickly, rudely, turns her back to him to take her first real look around.

First, she sees an NCU sweatshirt. That alone isn’t cause for concern. NCU is a huge school and, despite being more than five blocks away, they are pretty close to campus. 

Then, she sees the bottom of that sweatshirt:  _ NCU Swimming _ . The group that sweatshirt is drinking among are not all wearing NCU sweats, but enough of that athletic gear, combined with the lithe, muscular bodies she sees tells her all she needs to know.

That’s how Sam finds her as she comes back from the bathroom: turned around in her barstool, mouth slightly ajar and eyes wide. Kara’s unmistakable blonde ponytail bounces with her movement several feet and obstacles away. She hasn’t seen Lena yet and Lena suddenly can’t decide if she wants Kara to see her or if she wants to quickly make her exit.

“You knew, didn’t you?” Lena says, grabbing at Sam’s arm and quickly turning back around to face the bar.

“Knew what?” Sam asks, settling back onto her barstool next to Lena.

“You said you’ve been talking to the bartender?”

“Yeah....” A devilish smile springs to Sam’s face.

“Your friend the bartender said he knows all these swimmers here, that he went to NCU on a swimming scholarship, too.” Lena feels like she’s doing that whisper-yell thing Sam sometimes accuses her of. 

“So that’s why his body is so tight.”

“Sam. I thought we were going out to get my mind off of her.”

“I’m sorry, you’re right,” Sam says as she drops the grin and looks at Lena earnestly. “I shouldn’t have deceived you. We can leave right now if you want.”

Lena turns back around and looks over at Kara. Sam turns, too, and follows her gaze.

“That’s her, isn’t it? Are you thinking about how tight her body is, too?”

“Sam! Maybe.” In fact, after seeing Kara’s meets, her ‘tight body’ has semi-regularly crossed Lena’s mind. 

“Lena,” Sam starts, as they turn back around, “you’re one of the most disciplined people I know. If you want to keep yourself all the way buttoned up tonight, I’m sure you can. But, if you want to have another drink, and do a little eyefucking from across the room and then maybe have a quick makeout sesh in the bathroom, I don’t think anyone but me would be the wiser. You’re disciplined enough to be discreet, too.”

Sam’s characterization of her feels only partly true. Sure, Lena thinks, she’s disciplined in some parts of her life, mostly those that are academic. But lately, she feels so intemperate in her personal life. 

“I can’t decide whether you’re a great friend or a terrible friend.”

“That depends on you and where you take it from here.”

She looks back over her shoulder at Kara. “I want to get laid.”

“Great friend it is. Atta girl, Lena.” Sam raises her glass. “Then I’m going to work on getting laid, too.”

“Don’t get to work yet,” Lena says, grabbing Sam’s arm before she can flag the bartender down.

“I need to wait until the place clears out a bit before I can talk to her.”

“Why? Oh...right.”

They have one drink and then another. The bar is along a wall backed by a mirror and Lena occasionally flicks her eyes up to watch Kara. It’s still so crowded, but it fascinates Lena to see Kara amongst her team and friends socially, without knowing Lena is watching. It feels in some ways like the swim meets she’s attended. 

One time, she flicks her eyes up to see Kara’s head tilted back, draining a bottle of some flavorless light beer. 

When she flicks her eyes up again, she sees Kara in profile talking animatedly to a guy about her height. 

Another time, when Sam’s run off to the bathroom again, she watches Kara in the mirror for several minutes. She’s talking to a pair of girls this time, probably teammates because of their NCU attire. They’re both a couple inches shorter than Kara and looking up at her in a way that feels familiar not because she’s seen it before but because she knows she has looked at Kara like that before. It makes her clench her jaw for a moment, before she sees Kara get easily distracted by the guy she was talking to earlier.

She glances up again when she hears Kara’s laugh echo way too loudly in her ear. The bar must be clearing out a little if it sounds so clear. That, or Lena’s ear is especially in tune with Kara. Her head is tilted back and the column of her neck is exposed and Lena stares for so long that Sam catches her.

“I admire your willpower, Lena.”

“Why do you say that?” Lena says, dragging her eyes away to smile coyly at Sam.

“If I felt the way you look right now, I’d be humping her on that pool table over there, the rest of these people be damned.”

“There’s still a chance yet for you to hump someone on a pool table tonight.”

Sam looks over at the bartender, elbow deep in a cooler at the other end of the bar. “God, I hope so. Momma needs to get railed tonight.”

“Jesus, Sam.”

Lena turns her eyes to the mirror again and finds piercing blue eyes staring back at her. They hold each other’s gaze for a moment, her heart thundering in her chest, and then Kara raises her stupid arm to wave at her. Lena’s eyes go wide in the mirror and she shakes her head, hoping Kara gets it. Her hand pauses in the air for a moment before she uses it to adjust her glasses and fix her ponytail. Her eyes stay on Lena and Lena offers an anguished smile that Kara returns. 

Lena’s eyes skip across the mirror and catch Sam’s watching her as she watches Kara. 

“Oh honey.”

“Well, let’s hope I didn’t just ruin that,” Lena says, then tilts her head back to swallow the rest of her drink and get another.

Sam’s one of her best friends for more reasons than Lena can count, but if she had to give three, they would be: 1) that she makes Lena step out into the world (and most of the time it goes so well that reasons two and three don’t matter), 2) that she’s always Lena’s safety net, and 3) that when Lena is close to falling, Sam tries to help her find her balance. When she can’t do that, she’s able to distract Lena enough that the pain from the fall doesn’t hurt so much. 

They spend the next hour reminiscing over adolescent hookups and heartbreaks from boarding school and Lena finds herself not looking for blue eyes in the mirror as much as she was before.

About thirty minutes before last call, the bartender sidles back over and the break in conversation has her glancing into the mirror again. It’s much quieter now and she realizes that the swim team has cleared out. She doesn’t see Kara in the mirror, either, which she supposes makes sense since the team is gone, too. 

Now that it feels safe, she turns her body on the barstool and catches Kara leaning against the wall in the darkened hall in the back near the bathroom. The bright light from her phone illuminates her face. Lena leaves her drink and walks toward her. When she’s a few feet away, Kara looks up at her with soft eyes and a smile. She remains leaned up against the wall, back fully pressed against it and Lena leans her shoulder along the wall next to her, their bodies so close that she can feel Kara’s warmth. 

“Dr. Luthor.”

“Ms. Danvers.”

“I did not think a woman like you would set a dainty stiletto’d heel in a place like Al’s.” Her eyes scrape over the grimy floor they’re standing on. Kara’s wearing suede desert boots in a khaki color, which could very well be the butch-er version of her stilettos for how much she knows those boots cost. 

“I can live among the hoi polloi.”

“What did you just call me?”

She wants to reach out and touch her. At some point in the night, as Kara unwound, the sleeves of her patterned button-up were rolled up and her forearms taunt Lena. “Your dumb jock act is only cute some of the time.”

“You think I’m cute?” Kara looks very proud of herself. It’s a look Lena’s seen a few times during office hours, as she recites back some of what she remembers from class.

“I said sometimes.”

“Is now ‘sometimes’?”

Lena hesitates for a moment before she leans closer so that her body presses against Kara. Her patience and her discipline wear thin and she reaches out and touches Kara’s forearm. “In this shirt with those sleeves rolled up and in those jeans? Yes.”

“I’m glad I changed out of my sweats, then.” Kara watches Lena’s fingers move along her arm and flexes a little. 

“Those sweats do it for me sometimes, too,” Lena says, eyes looking up from where her fingers feel Kara’s arm moving to catch Kara’s eyes.

“Do what for you?” she whispers.

“Oh Ms. Danvers,” Lena says coyly, pulling back to lose contact. “I don’t want to get carried away.”

A look of disappointment flashes across Kara’s face. 

“Lena it’s just us. Look around. There’s no one here.” 

Sam, her fount of encouragement for the night, is perched at the end barstool that she’s been glued to the rest of the night, halfway to going home with the bartender after last call. She’s seen that look on her face before. And Kara’s right. There’s Sam, the bartender, an older couple playing pool in the back--certainly not university-affiliated with those leather jackets and stonewashed jeans.

“Can I get you a drink? Maybe we could sit down in that booth over there and talk?”

Lena feels exhausted. Her willpower has run dry and she can resist no more. She nods and minutes later they’re tucked into a back booth, Kara nursing a beer and Lena another whiskey on the rocks.

“So,” Kara starts, “uh...come here often?”

Lena shakes her head. “You are so corny.”

“I’m just practicing my dad jokes for later in life.”

“Are you planning on becoming a dad?”

Kara’s head tilts back in a laugh, then she looks at Lena and wriggles her eyebrows. “There’s a lot of ‘You can call me Daddy’ jokes running through my head right now.”

“Let’s not go there,” Lena says with a laugh of her own. 

“Ok, we’ll save it for some other time.”

“Can I ask you something?”

“Anything,” Kara answers, too quickly. 

“Why did you transfer to NCU?”

“I heard there was this beautiful physics professor…” 

“Kara.”

“I am capable of being serious, actually.” Lena’s not so sure of how long Kara’s ability to be serious sustains itself. It has never lasted more than ten minutes around her. “There’s no single reason for a big life decision like that, is there? NCU is better academically, I hated the coach at Metro State and he hated me, I missed my family.”

She can’t quite picture the version of herself that Kara’s describing, the Metro State version--disappointed with school, dwindling passion for a sport she loves, utterly alone. 

“Things are better at NCU so far?”

“Infinitely better,” Kara replies, picking at the damp label of her beer bottle. “Well...except for one of my professors.”

“Oh really?” Lena says with a smirk.

“Yeah, see she’s drop dead gorgeous, but it’s like she’s got this clear balloon around her. And she lets me inside of that clear balloon, but I can also see that there’s this other balloon inside that I just can’t get through. I can see that there’s some really amazing stuff in there. It’s hot,  _ red  _ hot, you might say. But I just can’t laser past that inner layer to get at the part that I really want.”

Lena starts shaking her head and smiling halfway through Kara’s explanation. “But when you do, everything inside her will heat up until it explodes. Is that right?” She feels the heat. It’s low and slow and it’s been building. 

“Exactly right.”

“You think you’re pretty clever, don’t you?”

Kara looks away bashfully, but then her eyes quickly look back up at Lena and she licks her lips. Suddenly the heat doesn’t feel so low and slow. 

“I think I pay attention in class more than you realize.”

“Who says I don’t realize it?”

The question hangs in the air for a minute as they both take sips of their drinks. Lena takes a quick look toward the bar and finds Sam leaned over it, whispering something in the bartender’s ear. 

“Have you had a good time tonight, Lena?” Kara asks softly. 

“I have, but I’m hoping the night is still young.”

Kara’s voice dips to a low register. “Are you?”

“Would you like to come home with me?” It’s pretty reckless, she knows, but Lena just can’t help it. 

“I really would.”

They take a rideshare back to Lena’s apartment, fingers twined together and silent the entire way there. Despite having her fair share of drinks, Lena feels suddenly sober. 

Had she known Kara would be in her kitchen when she woke up this morning she would have done about a million things during the day: empty the dishwasher, take the trash out, vacuum the area rug in the living room, organize the journals and papers and books scattered everywhere. When Kara walks in, Lena watches her eyes to see if they register disgust. But her eyes seem to take things in too quickly before they’re shining back on Lena and Lena only, like a spotlight.

It’s been a long time since she asked someone back to her apartment, and even longer since she’s had sex with someone. What worries her most, in the moment, though, isn’t the sex, it’s what comes after. Sleeping beside someone new feels like flinging her heart wide open. 

“You want a drink?” Lena asks as they stand just inside the door. 

“Water?”

“I’ve got that.”

Kara’s feet and then her eyes follow Lena to the fridge, as she holds a glass against the dispenser on the door. 

“Hey, that’s me,” she says, looking past Lena. 

“What?” Lena’s eyes find what Kara’s looking at. That stupid swim team schedule magnet she’d picked up on a whim at the first meet. (And which had dictated many of her weekend plans ever since, but she’s reluctant to let her brain admit that.)

“Didn’t know you were a fan.”

“Call it a budding interest.”

Kara picks the glass of water out of Lena’s hands. She’s not exactly pinning Lena to the fridge, but there’s not much room to move. Not that she wants to. When the water’s set on the counter, Kara’s fingers graze across Lena’s. She licks her lips and then her eyes drop to Lena’s lips, and back to Lena’s eyes, in what feels like neverending repetition. 

“Can I…?”

Lena nods and leans forward just the barest bit. Her eyelids flutter closed and she can feel Kara’s breath on her lips. Kara reaches up to cradle her jaw and Lena’s ready for her to deliver the softest, most anticipated kiss of her 22 years. 

And then Kara’s head pulls back and her eyes are on the fridge again.

“The only way you could have gotten that was at a meet.” Kara says, pointing to the swim team magnet.

“It was...you were...I didn’t…,” the more Lena sputters the more Kara’s smirk turns into a smile. “I didn’t realize a body could move that way,” she finally ends up saying. 

As soon as Lena says it, the smile disappears. “Guess you’ll have to keep coming. Do some research on the physics of swimming.”

Lena just nods and leans forward again. 

“I could show you other ways my body moves,” Kara whispers, lips ghosting from Lena’s ear down to her neck as Lena tilts her head back and digs her fingers into the base of Kara’s scalp. “Maybe show your body how to move that way, too.”

“Kara.” It’s said with a little bit of a scold and a little bit of a giggle and Lena digs her fingers in a little harder. 

“What? You set me up for it.” Lena can only feel Kara’s smile against her neck. 

“Are you going to kiss me or are you going to keep running your mou…”

Kara’s lips are on her in a rush before she can finish her sentence. Her lips taste faintly like beer as they press firmly into her and their noses knock for an instant before they find their fit. And when they do, when the frantic pace of the initial kiss, then the second, then the third as their mouths open to one another -- when that frantic pace ends, Kara’s strong hands are gently cupping her face and everything feels so soft. Her heart feels like it’s beating everywhere, outside her body even.

And then Kara’s actually pinning Lena against the fridge, the cold metal surface of it at her back and Kara’s warm body at her front. Kara’s body presses into hers, their lips meet and then Kara’s lips capture her bottom lip and suck. In an instant, Lena’s hands find purchase beneath Kara’s shirt, gripping at the hot, taut skin beneath. She pushes back against Kara and opens her mouth, licking into Kara’s. There’s a gasp and a groan and it’s impossible to tell who does what. 

When Kara pulls back, her lips glisten and her pupils are dark. She glances at the magnet again and then back at Lena. 

“I’ve been wanting to do that since the moment you kneeled down beside my desk.” She’s a little breathless when she says it. 

“And I’ve been wanting you to fuck me since I saw you in that blue oxford the second week of class.” Lena almost says ‘ _ since I saw you warming up on the pool deck for your first race of the year _ ,’ but she catches herself in time. Yes, Kara now knows she’s been to a meet, but she doesn’t want Kara to know just how enraptured she was with her during that meet. 

“Lena. Dirty!” Kara steps back in mock horror, hand on her chest.

But Lena won’t let her get too far. She laughs and pulls Kara by the forearm back into her. When Kara’s close enough, Lena leans in to whisper in her ear, “I wouldn’t mind if you wanted to talk a little dirty, too.”

The wet lips and dark pupils are back, but they seem even darker now. 

“Dirty like: I want you to go into your room, take off all your clothes, and wait on your knees with your hands gripping the headboard until I’m ready for you?”

Lena licks her lips and her chest heaves as she breathes out audibly. “Ok,” she says with a gulp.

Kara grabs her hands. “No wait,” she laughs. “I mean,  _ yes _ , I’ll definitely keep that headboard idea in mind, and the waiting on your knees part, that seems hot. But maybe not tonight?”

“Are you saying you don’t want to have sex?” Lena suddenly feels like she’s tiptoeing a highwire.

“No. No no no,” Kara says, softly stroking Lena’s palm, sensing her worry. “Just...maybe something that’s a little less 50 Shades of Grey for tonight,” she ends with a genuine smile.

She thinks it’s probably in Kara’s nature to do this -- to find this way of saying something that could devastate and following it up with something so serene. And Lena’s not upset by it, necessarily, but finds herself occasionally muddled by it all.

Still, she recovers quickly enough. “That’s hardly 50 Shades of Gray, but if you don’t stop teasing me and get to work, I’m going to take care of myself, Kara Danvers.”

“I’d like that actually,” Kara whispers against her lips, then captures them again. Kara’s hands are on her hips and then her hips are pulled in so close to Kara’s body that Kara’s thigh slips between hers and before she realizes it, she’s grinding up against it and biting into Kara’s kiss.

When they break, Lena’s chest is heaving and Kara’s kissing down her neck and her hands are moving to the button of Lena’s jeans. 

“Kara,” she moans in a voice that she barely recognizes as her own. Her hands move down Kara’s arms, from her shoulders to her biceps and then to cover and slow her hands. Somewhere in the back of her mind, she thinks about whether Kara could pick her up. 

“You’re so hot,” Kara says as she scrapes her teeth across Lena’s neck. If Lena weren’t so insanely turned on, she might laugh at that. It’s not the first time and it won’t be the last that Kara’s sounded more like a teenage boy than an adult woman. 

She pushes her hands against Kara’s chest. “Kara, wait.”

Kara’s off her in an instant, eyes transforming from dark and glazed to warm and concerned immediately. “Are you ok?”

Lena looks up into her eyes. She likes this, how close they are. She likes that she has to tilt her head up when they’re this close so that she can look into Kara’s eyes, so that she can kiss her. 

“I want to do this in a bed, not against my fridge.”

“Lead the way, Dr. Luthor.” Kara says, spinning their bodies but grasping Lena’s hand so that she can pull Kara toward the back hallway. 

“No more Dr. Luthor tonight, ok?”

“As you wish,” Kara says. Lena can hear her smiling, even if she can’t see her. 

Lena pushes Kara so that she’s sitting on the edge of the bed, flicking her boots off with her feet, while Lena kicks off her heels and peels herself out of her jeans. Before Kara can do anything more than unbutton her pants, Lena climbs into her lap, straddling her and kissing the column of her throat. When Kara feels the graze of Lena’s teeth through her shirt and into the muscle of her shoulder, she palms two hands full of Lena’s ass and thrusts up into her with a groan. 

And then Kara stands up, with Lena’s legs wrapped around her body so that Lena can only hold on and maintain her own balance enough not to tilt them both off-balance. Kara turns with the strength of 1,000 men and slowly settles Lena onto her back on her comforter, arms flexing the whole way down. 

“So beautiful,” Kara whispers. Her eyes drag across Lena’s body and it sounds like Kara’s whispering to herself. While Kara stands, she takes a moment to pull her jeans off, hopping out of one leg, then the other while Lena laughs in one moment and stares at her strong thighs in the next. 

And then Kara’s crawling toward her on the bed and pulling Lena up to sit. 

“Can I take this off?” Kara asks, fingers dancing over Lena’s silky tanktop. 

If she’d known the night would end in this, she would have worn her new matching set of lingerie and suffered through the way that the bra digs into her back, just so that she could see Kara’s reaction to it in this moment. 

The current circumstances, though, are exactly how she’d fantasized Kara might react. Kara’s eyes dip down to her cleavage and then, as though she’s been caught doing something she’s not supposed to, they whip back up to look into Lena’s eyes. 

“It’s ok for you to look,” Lena says after she captures Kara’s bottom lip in a wet kiss.

Kara leans back and ogles this time. “I’ve been waiting all semester to meet you two,” she says, as she reaches a hand up to palm Lena’s breast. 

Lena tilts her head back in a full-on, body-shaking laugh. “How can you say something so sexy in one moment and so ridiculously goofy in another, Kara Danvers?” 

“Sorry,” Kara says, tilting her head to the side and grinning. 

Lena finds herself tilting her head to match Kara’s angle. She leans in and strokes Kara’s jaw with her thumb before laying a slow, chaste kiss on her lips. “Don’t be sorry for that, ok?” She whispers. “It’s one of the things I like most about you.”

Kara presses her forehead to Lena’s and closes her eyes before she whispers in a voice that’s barely there, “Ok.”

“Can I take these off, or will you be blind?” Lena asks, her hands reaching for Kara’s glasses.

“Oh. Yeah,” Kara pulls them off herself. “I forget they’re on most of the time. As long as you don’t end up across the room for some reason, I’ll be fine.”

As she leans to put her glasses on the bedside table, she pushes Lena flat on her back and their bodies twist so that Kara can settle between her hips. 

Her head dips to gently suck against the pale skin of Lena’s neck, then to lave her tongue down the column of her throat to the blush on her chest. Her lips then wrap around the dusty pink of one of Lena’s nipples, while Kara’s hand tickles and trails down Lena’s stomach to the wetness between her legs. 

Lena suddenly feels frenzied and like the entire night has been foreplay, all the way back to catching Kara’s eyes in the mirror at the bar. 

“Inside,” she whispers hotly, grabbing at Kara’s hand and positioning it at her entrance. “Two. Please.” Her hips roll up with a mind of their own, attempting to speed Kara’s slow pace. 

They fumble for a minute, knocking knees and bumping foreheads once as they try to reposition their bodies. Sex for the first time, and the second, and the third, and maybe for a little while longer is like learning a new subject in, say, a 300-level class. You’ve got some background knowledge, you’ve taken a 100-level class, at the very least. But at the beginning, the 300-level class takes a moment to square with what you’ve learned in that 100-level class. And even when it does square itself, there’s still the fact that you’re contending with newness at every step along the way. Eventually it settles into routine, but it takes a while. There’s something thrilling in that.

“Please, Kara, go faster. Harder.” Kara dutifully follows orders and there’s a wicked, wet sound her fingers make as they move in and out quickly that Lena might be embarrassed by if Kara weren’t looking at her with such reverence. Her gaze on Lena gets to be too much and Lena slips her eyes closed and tilts her head back. Kara takes that as an invitation and moves her face so close that her forehead touches Lena’s cheek. 

When her orgasm hits, Lena feels transcendent. Her head flops to the side, away from Kara and her mouth opens and opens and opens. With each drop in her jaw the oxytocin builds and her diaphragm pushes out garbled, wailing noises. And in the final throes of it, her body shakes and her thighs clasp shut capturing Kara’s hand.

It takes several minutes for her to recover. Kara’s wet fingers stroke back up her body, leaving a trail of conquest. Her leg flops over Lena’s to intertwine with her. The skin of her forehead where sweat beads at her hairline presses against Lena’s forehead. But, once the clenching of her body and the tingles of her orgasm dwindle, the feeling that she’s most enamored with is Kara’s eyelashes whispering against her skin. 

“I can’t even describe how much I like seeing you like this, Lena.” Kara’s voice is hoarse and it sparks a second wave of arousal in Lena.

“Our vibrational frequencies are running in sync tonight,” Lena whispers to the ceiling, eyes still closed. 

Kara laughs, then drums a finger on Lena’s solar plexus. “Pop.”

“Pop, indeed,” Lena giggles, turning into Kara so that she can see the way Kara is looking at her again. It feels less scary to meet her gaze now. “Are you going to show me how your body moves?”

Kara’s eyes go dark. “You like that?”

“I like that. I want to feel you coming while you move on top of me.”

“Oh, that mouth. Where did it come from, Lena?”

“I could say the same for you.”

Kara grinds her body against Lena’s for what alternately feels like seconds and then hours. Her muscles tighten and dig into Lena’s soft body, which just spurs on Lena’s encouragement of her as she winds her hips and pushes their bodies together. 

“That’s it, Kara,” she says breathily.

Kara stops suddenly and pulls back to look at her. “Can you come like this?”

“Probably not,” Lena starts, and before she can finish what she wants to say she feels Kara trying to move off of her. 

“No, stay, please,” she whines. “I like this. A lot.”

Kara looks at her with hooded eyes and nods before resuming. 

It seems that now that she knows Lena won’t be joining her in release, her movements are quicker and more selfish. Her head falls into the crook of Lena’s neck and Lena can hear every breath she takes. It’s not long before her labored breathing adds a quiet grunt as punctuation. 

“Are you going to come for me, Kara?”

Kara whines at that and Lena’s hips jump up in reaction to take a little of her own pleasure. At her climax, when her hips are moving recklessly and without rhythm, she emits a broken  _ oh _ with every wheezing breath she takes. Lena’s fingers dig into her lower back and then her hips, spurring her on. 

Finally, Kara’s body slumps over hers, nose pushing into her neck. Lena runs her hand up Kara’s back and strokes into the soft hairs at the base of her neck.

Soon, Lena finds her mind shutting off and her eyes fluttering shut. Kara’s rhythmic breathing atop her indicates that Kara’s done the same. 

It could be minutes later, or a couple hours later. It’s still dark out, either way, when Kara’s body shifts and Lena’s eyes blink open to find Kara looking at her.

“Can I go down on you?” she asks, body already shuffling down toward the end of the bed.

“Please,” Lena hears herself say sleepily, her id responding before the rest of her psyche can kick into gear.

By the time Kara’s brought her to orgasm twice with her mouth, Lena’s convinced that Kara was born to go down on her. Maybe being a swimmer has something to do with her talents? Practiced breathing, eyes focused, shoulders strong as they propel the movement of the two fingers curling inside of Lena. There’s a joke in there somewhere about swimmers being used to getting wet, but she can’t and doesn’t want to finish that train of thought now. 

After Kara’s lips have kissed either side of her inner thighs, Lena desperately wants to see Kara come undone from the same perspective. After a few minutes of finding the right combination of movements, Kara becomes the most vocal she has all night. It still isn’t much, but it spurs Lena on a bit more. There’s a  _ right there _ , followed by a drawn out groan. 

“God, Lena, that feels good,” she says quickly, as Lena can feel her getting closer. When Lena looks up, she can see Kara clenching her abs and straining to look down at her. “I see you rolling your hips,” Kara whispers with a little gasp at the end, “do you want to take care of yourself?”

Lena’s eyes brighten as she recalls her words from earlier and the way that Kara reacted when she’d suggested she touch herself if Kara wouldn’t. She slips a hand down between her legs and is soon desperately rocking against it as Kara’s thighs shake and jolt around her head.

When Kara comes, it’s with a strained, low moan. She surfaces with a gasp, like she’s been holding her breath underwater. In some ways, it seems out of character to Lena. Outside of the bedroom, Kara’s typically loud, silly, glowing with energy. But then maybe inside of the bedroom, Lena’s a bit out of character, too. Outside, she’s disciplined, restrained, and reserved -- “buttoned up” as Sam likes to say. Inside, she’s unruly, demanding, and liberated. It feels good to know someone so intimately. Scary, she thinks, but good. 

When she climbs back up Kara’s body, Lena presses against the skin of Kara’s heaving chest.

“Ever had this thing, Kara starts, her hand against Lena’s spine tracing it up and down gently, “after you come really hard where it’s like the sound of static in your ears? What’s that about?” 

“I don’t know.” 

“You’re supposed to explain the beauty of the world to me, Lena.”

She lifts her head up from Kara’s chest where she’d been listening to her heartbeat and Lena pulls Kara into a kiss. “I think we’ll have to do more research.”

\--

“Good morning”

Kara’s blue eyes are the first thing she sees. Lena’s not sure what time it is, but her alarm hasn’t gone off and she’s sure she plugged her phone in last night, so it’s definitely before seven, which also means they’re only slept for a few hours. 

Lena’s eyes blink open slowly at first, accommodating the light in the room. A soft, sleepy smile pulls at her as she awakens. Kara’s hand tucks a wild strand of Lena’s hair behind her ear. 

“Hi.” Lena whispers, once she’s found her bearings. 

“So.”

“So.”

“In the light of day, we’re not freaking out?”

Lena nods. “Not freaking out.”

“I can freak out with you if you want.”

Lena shakes her head and smiles. “No, just...” she gets serious suddenly, “no one can know about this.”

Kara mimes closing her mouth, locking it, and tossing a key over her shoulder.

“I’m serious, Kara.”

“I know,” Kara says, matching Lena’s tone. “No one will know.”

Lena nods but then she has to look away, worried about what she might say or do next. Kara’s fingers trace down her spine, just like they did last night, and she tucks her head under Kara’s chin and presses her lips to the pulse beating in her neck. 

She can feel in this moment the building of an impossible choice to come. It’s a choice she can ignore until the last possible moment, or that she can allow to eat her alive until it forces her to choose far sooner than she needs to.

She feels Kara’s warm breath against the crown of her head and pulls back to look at her.

“The sun really does hit your eyes in a way that’s devastating,” Kara says.

“I could say the same for you. Physics does explain all the beauty the eye can see, you know.”

“I’ve heard that once or twice,” Kara’s got a devilish grin on her face as she hoists herself up to straddle Lena’s thighs and look down at her. 

“Does physics explain how beautiful you are, Lena?” she asks, leaning down to draw a soft kiss from her lips. 

“Does it explain the blush in your cheeks that flows down the cords of your neck and blooms in your chest?” Kara’s lips kiss a trail to follow the hot pink path of Lena’s blush. 

“Will it explain the way your skin feels against mine?” Kara’s weight is fully atop Lena, chests connected, hips touching, legs tangled together. 

“Or that smile that’s only for me?” Kara looks up at her. “Yep, that one.”

“What of the math that explains the feel of your thighs around my head?” she asks, pulling one of Lena’s legs to rest on her shoulder as she settles between them. 

“Shhh Keats,” Lena laughs and Kara can feel her body quiver. “Use that mouth for something other than talking.”

“Right-o Newton.” 

**Author's Note:**

> This story is drawn from two sources of inspiration:  
> 1) This fic prompt found on Tumblr: "You're my professor and this is your first year teaching and we're practically the same age can I stay after class so that you can help me with this thing I don't understand." It's been long enough since I saw this prompt that I don't remember its source. My bad.  
> 2) Harvard's Spring 2021 freshman seminar titled none other than "The Interaction of Light with the World." I don't know jack about physics any more, but I've had a good time doing research as I write. For the most part, I'm trying to stay away from the stuff that's not making any sense to my pea-sized science brain. I hope, for those like me, that it makes enough sense that you can follow along. And, for those not like me who have been blessed with legitimate science brains, I hope I'm not in over my head!


End file.
